Power-receiving device, wireless power-feeding system including power-receiving device, and wireless communication system including power-receiving device

ABSTRACT

When a portable electronic appliance is provided with two systems, a wireless power-feeding system and a wireless communication system, each system requires two power-receiving devices, a coil and an antenna, leading to a problem of increased electronic appliance size and cost. Wireless power feeding employs the resonance method and uses a resonance coil using the resonance method and a power-receiving coil that receives power from the resonance coil. At least one of the resonance coil and the power-receiving coil can also be used as an antenna for wireless communication. Thus, a power-receiving device that can be used for two systems, wireless power feeding and wireless communication, can be provided.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a power-receiving device, a wirelesspower-feeding system including the power-receiving device, and awireless communication system including the power-receiving device.

2. Description of the Related Art

Various electronic appliances have spread and a variety of products isshipped to the market. In recent years, the spread of portableelectronic appliances such as cellular phones and digital video camerasis apparent.

A cellular phone or a digital video camera has a built-in batteryserving as a power storage means. Currently, such a battery is charged,in most cases, by bringing it in direct contact with a household ACpower source serving as a power-feeding means. In view of this, researchand development of methods of wirelessly charging batteries or feedingelectricity to loads for improved convenience have advanced. Typicalexamples of methods for wireless power-feeding systems include theelectromagnetic coupling method (also called electromagnetic inductionmethod), the radio wave method (also called micro wave method), and theresonance method (also called magnetic resonance method).

A wireless power-feeding system using the electromagnetic couplingmethod cannot yield high transmission efficiency when a power-feedingcoil in a power-feeding device and a power-receiving coil in anelectronic appliance are displaced. Accordingly, a power-feeding deviceequipped with a plurality of power-feeding coils, and a technique tomove the power-feeding coil so that it can be aligned with thepower-receiving coil have been developed (see Patent Document 1, forexample).

Wireless power-feeding systems using the resonance method have attractedattention and their research and development have been promoted becausethey yield high transmission efficiency, for middle and long distanceuse (see Patent Document 2, for example).

On the other hand, more and more portable electronic appliances such asrecent cellular phones and smartphones function as wireless IC cardshaving applications such as electronic money. Since wireless IC cardsneed a wireless communication function, these portable electronicappliances have a built-in antenna for communication (see PatentDocument 3, for example).

REFERENCE

-   [Patent Document 1] Japanese Published Patent Application No.    2010-273473-   [Patent Document 2] Japanese Published Patent Application No.    2010-252468-   [Patent Document 3] Japanese Published Patent Application No.    2008-210301

SUMMARY OF THE INVENTION

Conventionally, when a portable electronic appliance is provided withtwo systems, a wireless power-feeding system (hereinafter also calledwireless power feeding) and a wireless communication system (hereinafteralso called wireless communication), each system requires twopower-receiving, devices such as a coil and an antenna, leading to aproblem of increased electronic appliance size and cost.

In view of this, it is an object of one embodiment of the presentinvention to provide a power-receiving device that yields hightransmission efficiency and can be used for two systems, wireless powerfeeding and wireless communication.

One embodiment of the present invention employs the resonance method forwireless power feeding and uses a resonance coil using the resonancemethod and a power-receiving coil that receives power from the resonancecoil. At least one of the resonance coil and the power-receiving coilcan also be used as an antenna for wireless communication. Thus, apower-receiving device that can be used for two systems, wireless powerfeeding and wireless communication, can be provided. The details will begiven below.

One embodiment of the present invention is a power-receiving deviceincluding: a power-receiving resonance coil generating a firsthigh-frequency voltage by a resonance method; and a power-receiving coilgenerating a second high-frequency voltage by using electromagneticinduction between the power-receiving coil and the power-receivingresonance coil. At least one of the power-receiving resonance coil andthe power-receiving coil receives a signal on a carrier wave or anamplitude modulation wave by using electromagnetic induction. Thepower-receiving coil is electrically connected to a wirelesspower-feeding unit and a wireless communication unit. The wirelesspower-feeding unit includes a rectifier circuit rectifying the secondhigh-frequency voltage generated by the power-receiving coil, aconverter electrically connected to the rectifier circuit, and a loadreceiving power converted by the converter. The wireless communicationunit includes a reception circuit receiving the signal, apower-receiving controller controlling the signal received by thereception circuit, a modulation transistor electrically connected to thepower-receiving controller, and a load modulation element electricallyconnected to the modulation transistor. The wireless power-feeding unitand the wireless communication unit are integrated.

One embodiment of the present invention is a power-receiving deviceincluding: a power-receiving resonance coil generating a firsthigh-frequency voltage by a resonance method; and a power-receiving coilgenerating a second high-frequency voltage by using electromagneticinduction between the power-receiving coil and the power-receivingresonance coil. At least one of the power-receiving resonance coil andthe power-receiving coil receives a signal on a carrier wave or anamplitude modulation wave by using electromagnetic induction. Thepower-receiving coil is electrically connected to a wirelesspower-feeding unit and a wireless communication unit. The wirelesspower-feeding unit includes a rectifier circuit rectifying the secondhigh-frequency voltage generated by the power-receiving coil, aconverter electrically connected to the rectifier circuit, and a loadreceiving power converted by the converter. The wireless communicationunit includes a reception circuit receiving the signal, apower-receiving controller controlling the signal received by thereception circuit, a modulation transistor electrically connected to thepower-receiving controller, and a load modulation element electricallyconnected to the modulation transistor. The power-receiving resonancecoil and the power-receiving coil are placed to at least partly overlapwith each other. The wireless power-feeding unit and the wirelesscommunication unit are integrated.

One embodiment of the present invention is a wireless power-feedingsystem including the above-described power-receiving device and apower-transmitting device. The power-transmitting device includes ahigh-frequency power source generating a third high-frequency voltage, apower-transmitting coil receiving the third high-frequency voltage, anda power-transmitting resonance coil generating a fourth high-frequencyvoltage by using electromagnetic induction between thepower-transmitting resonance coil and the power-transmitting coil. Thefirst high-frequency voltage is generated by magnetic resonance betweenthe power-transmitting resonance coil and the power-receiving device.

One embodiment of the present invention is a wireless communicationsystem including the above-described power-receiving device and acommunication device. The communication device includes an oscillatorgenerating a carrier wave, a modulation circuit converting the carrierwave into an amplitude modulation wave, a matching circuit forsubjecting the amplitude modulation wave to matching, and an antennaelectrically connected to the matching circuit. A signal on a carrierwave or an amplitude modulation wave is transmitted and received withelectromagnetic induction between the antenna and the power-receivingdevice.

One embodiment of the present invention can provide a power-receivingdevice that yields high transmission efficiency and can be used for twosystems, wireless power feeding and wireless communication.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1C are diagrams for describing a structure according toEmbodiment 1.

FIG. 2 is a diagram for describing a structure according to Embodiment1.

FIG. 3 is a diagram for describing a structure according to Embodiment1.

FIGS. 4A to 4C are diagrams for describing a structure according toEmbodiment 2.

FIGS. 5A to 5E are diagrams for describing a structure according toExample 1.

FIG. 6 is a diagram for describing the results obtained in Example 1.

FIGS. 7A to 7D are diagrams for describing a structure according toExample 2.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention will be described below withreference to the drawings. Note that the embodiments can be implementedin various different ways. It will be readily appreciated by thoseskilled in the art that modes and details of the embodiments can bemodified in various ways without departing from the spirit and scope ofthe present invention. The present invention therefore should not beconstrued as being limited to the description of the embodiments. Notethat in structures of the present invention described below, referencenumerals denoting the same portions are used in common in differentdrawings.

Note that the size and the like of each object shown in the drawings inthe embodiments are exaggerated for simplicity in some cases. Eachobject therefore is not necessarily in such scale.

Note that, in this specification, the terms “first” to “n-th (n is anatural number)” are used only to prevent confusion between components,and thus do not limit numbers.

Embodiment 1

This embodiment describes a power-receiving device according to oneembodiment of the present invention with reference to FIGS. 1A to 1C,FIG. 2, and FIG. 3.

FIG. 1A is a plan view showing a power-receiving device viewed from afirst surface side. FIG. 1B is a plan view showing the power-receivingdevice viewed from a second surface side. FIG. 1C is a cross-sectionalview taken along dashed line X1-Y1 in FIGS. 1A and 1B.

The power-receiving device shown in FIGS. 1A to 1C includes a substrate102, a power-receiving resonance coil 104 formed over the first surfaceof the substrate 102, a capacitor 106 connected to the power-receivingresonance coil 104, and a power-receiving coil 108 formed over thesecond surface of the substrate 102.

A glass epoxy substrate, a glass composite substrate, a paper-phenolicsubstrate, or a flexible substrate such as a film can be used as thesubstrate 102.

The power-receiving resonance coil 104 formed over the first surface ofthe substrate 102 is brought into resonance (the resonance method) witha power-transmitting resonance coil (not shown in FIGS. 1A and 1B) in apower-transmitting device to generate a first high-frequency voltage;thus, power transmission is achieved. The power-receiving resonance coil104 is a coil of wires made of a low-resistance material such as copper,silver, or aluminum. The use of a low-resistance material for thepower-receiving resonance coil 104 is preferable because it enablespower to be transmitted with high efficiency. Note that the number ofturns of the coil can be adjusted as appropriate.

The capacitor 106 is an element provided to adjust the self-resonantfrequency of the power-receiving resonance coil 104. Note that thecapacitor 106 is not necessarily provided in the case where floatingcapacitance between the coil wires of the power-receiving resonance coil104 eliminates the need for adjustment of the self-resonant frequency ofthe power-receiving resonance coil 104. When the capacitor 106 is notprovided, both ends of the coil wires of the power-receiving resonancecoil 104 are open.

Power transmission to the power-receiving coil 108 formed over thesecond surface of the substrate 102 is achieved by generating a secondhigh-frequency voltage with electromagnetic induction between thepower-receiving coil 108 and the power-receiving resonance coil 104formed over the first surface of the substrate 102. It is preferablethat the power-receiving resonance coil 104 and the power-receiving coil108 be placed to at least partly overlap with each other with thesubstrate 102 therebetween, and the number of turns of thepower-receiving coil 108 be, smaller than that of the power-receivingresonance coil 104. Such placement and structure enhance magneticcoupling between the power-receiving coil 108 and the power-receivingresonance coil 104 and increase particularly short-distancepower-transmission efficiency in the case of power feeding using theresonance method. Thus, the power-receiving device can receive powertransmitted to the power-receiving resonance coil 104 with highefficiency.

The following describes the specific structure of the power-receivingdevice shown in FIGS. 1A to 1C and a wireless power-feeding system usingthe power-receiving device with reference to FIG. 2.

Note that a portion having the same function as that of any component inFIGS. 1A to 1C is denoted by the reference numeral of that component andits detailed description is omitted.

FIG. 2 is a block diagram showing a wireless power-feeding system usingresonance between the power-receiving device shown in FIGS. 1A to 1C anda separately provided power-transmitting device 250 (the resonancemethod). FIG. 2 shows electromagnetic power transmission achieved byresonance, between a power-transmitting resonance coil 254 in thepower-transmitting device 250 and the power-receiving resonance coil 104in a power-receiving device 200. In the block diagram of FIG. 2, thecircuits in the power-receiving device 200 and the power-transmittingdevice 250 are classified according to their functions and shown asindependent units. Note that it is actually difficult to completelyseparate the circuits in the power-receiving device 200 and thepower-transmitting device 250 functionally; therefore, one circuit canhave a plurality of functions. In other words, a plurality of circuitscan achieve a function corresponding to that of one unit.

The power-receiving device 200 shown in FIG. 2 includes thepower-receiving resonance coil 104 generating the first high-frequencyvoltage by the resonance method, and the power-receiving coil 108 thesecond generating high-frequency voltage with electromagnetic inductionbetween the power-receiving coil 108 and the power-receiving resonancecoil 104. At least one of the power-receiving resonance coil 104 and thepower-receiving coil 108 receives a signal on a carrier wave or anamplitude modulation wave by using electromagnetic induction.

The power-receiving coil 108 is electrically connected to a wirelesspower-feeding unit 230 and a wireless communication unit 240. Thewireless power-feeding unit 230 includes a rectifier circuit 208rectifying the second high-frequency voltage generated by thepower-receiving coil 108, a DCDC converter 210 electrically connected tothe rectifier circuit 208, and a load 212 receiving power converted bythe DCDC converter 210. The wireless communication unit 240 includes areception circuit 214 receiving a signal that has been received by atleast one of the power-receiving resonance coil 104 and thepower-receiving coil 108, a reception controller 220 controlling asignal that has been received by the reception circuit 214, a modulationtransistor 206 electrically connected to the reception controller 220,and a load modulation element 204 electrically connected to themodulation transistor 206. The wireless power-feeding unit 230 and thewireless communication unit 240 are integrated.

The power-receiving device 200 may include a directional coupler 202.The directional coupler 202 separates a modulation signal on apower-transmission carrier from the carrier and transmits the modulationsignal to the reception circuit 214. Note that the directional coupler202 is not necessarily provided. For example, when high power istransmitted, it is preferable to provide the directional coupler 202 asshown in this embodiment.

As described above, in the power-receiving device 200, the wirelesspower-feeding unit 230 and the wireless communication unit 240 areintegrated, and the power-receiving coil 108, which is included in thepower-receiving device shown in FIG. 1, is connected to a plurality ofcircuits and devices.

The power-transmitting device 250 includes a capacitor 252, thepower-transmitting resonance coil 254, a power-transmitting coil 256,and a high-frequency power source 258.

The following describes the operation of the power-receiving device 200and power-transmitting device 250.

Power transmission to the power-receiving device 200 is achieved byresonance between the power-receiving resonance coil 104 and thepower-transmitting resonance coil 254 in the power-transmitting device250. Power transmitted to the power-receiving resonance coil 104 istransmitted to the power-receiving coil 108 by the electromagneticcoupling method.

Power transmitted to the power-receiving coil 108 is transmitted to theload 212 via the directional coupler 202, the rectifier circuit 208, andthe DCDC converter 210. In other words, power transmitted to thepower-receiving coil 108 is transmitted to the wireless power-feedingunit 230.

Note that the DCDC converter 210 converts a current that has beenrectified by the rectifier circuit 208 into a desired current (power)needed for the load 212 located at the subsequent stage.

The load 212 can be any device that can operate when receiving powerwirelessly. Examples of such a device include a battery, an electricmotor, a bulb, and an electronic device operating with a battery, suchas a cellular phone.

The directional coupler 202 is electrically connected to the receptioncircuit 214 in the wireless communication unit 240. However, in thewireless power-feeding system, the wireless communication unit 240 inthe power-receiving device 200 does not function.

In the power-transmitting device 250, the frequency (oscillationfrequency) of an alternating-current (AC) signal output from thehigh-frequency power source 258 is applied to the power-transmittingcoil 256. Power transmitted to the power-transmitting coil 256 istransmitted to the power-transmitting resonance coil 254 by theelectromagnetic coupling method. The power-transmitting resonance coil254 is provided with the capacitor 252. The self-resonant frequency ofthe power-transmitting resonance coil 254 can be adjusted using thecapacitor 252.

Note that the frequency of an AC signal output from the high-frequencypower source 258 is not limited to a particular frequency and can be anyoscillation frequency with which the power-transmitting device 250 cantransmit power to the power-receiving device 200 by the resonancemethod. The oscillation frequency in the resonance method can be used,for example, in a frequency band of several kilohertz to severalgigahertz.

As described above, power generated with the high-frequency power source258 in the power-transmitting device 250 can be transmitted withresonance between the power-transmitting resonance coil 254 and thepower-receiving resonance coil 104 in the power-receiving device 200(the resonance method). Thus, unlike wireless power-feeding using theelectromagnetic coupling method, wireless power-feeding using theresonance method can widen an area where power can be fed and achievehigh transmission efficiency.

Next, a wireless communication system using the power-receiving device200 in FIG. 2 will be described with reference to FIG. 3.

Note that a portion having the same function as that of any component inFIGS. 1A to 1C and FIG. 2 is denoted by the same reference numeral asthat of the component and its detailed description is omitted.

FIG. 3 is a block diagram showing a system of wireless communicationbetween the power-receiving device 200 shown in FIG. 2 and a separatelyprovided communication device 270. In the block diagram of FIG. 3, thecircuits in the power-receiving device 200 and the power communicationdevice 270 are classified according to their functions and shown asindependent units. Note that it is actually difficult to completelyseparate the circuits in the power-receiving device 200 and the powercommunication device 270 functionally; therefore, one circuit can have aplurality of functions. In other words, a plurality of circuits canachieve a function corresponding to that of one unit.

The power-receiving device 200 shown in FIG. 3 includes thepower-receiving resonance coil 104 generating the first high-frequencyvoltage with the resonance method, and the power-receiving coil 108generating the second high-frequency voltage with electromagneticinduction between the power-receiving coil 108 and the power-receivingresonance coil 104. At least one of the power-receiving resonance coil104 and the power-receiving coil 108 receives a signal on a carrier waveor an amplitude modulation wave by using electromagnetic induction.

The power-receiving coil 108 is electrically connected to a wirelesspower-feeding unit 230 and a wireless communication unit 240. Thewireless power-feeding unit 230 includes a rectifier circuit 208rectifying the second high-frequency voltage generated with thepower-receiving coil 108, a DCDC converter 210 electrically connected tothe rectifier circuit 208, and a load 212 receiving power that has beenconverted by the DCDC converter 210. The wireless communication unit 240includes a reception circuit 214 receiving a signal that has beenreceived by at least one of the power-receiving resonance coil 104 andthe power-receiving coil 108, a reception controller 220 controlling asignal that has been received by the reception circuit 214, a modulationtransistor 206 electrically connected to the reception controller 220,and a load modulation element 204 electrically connected to themodulation transistor 206. The wireless power-feeding unit 230 and thewireless communication unit 240 are integrated.

The power-receiving device 200 can include a directional coupler 202.The directional coupler 202 separates a modulation signal on apower-transmission carrier from the carrier and transmits the modulationsignal to the reception circuit 214. The directional coupler 202 iselectrically connected to the reception circuit 214 and the receptioncontroller 220. The reception circuit 214 can be composed of a pluralityof circuits such as a low pass filter (a type of filter circuit), anamplification circuit, and a demodulation circuit.

Note that while wireless communication is carried out, the wirelesspower-feeding unit 230 does not function. Note that the wirelesspower-feeding unit 230 may have a function of, for example, referringthe amount of remaining battery or the like according to an instructionof a received signal and sending it back.

A communication device 270 includes an antenna 272, a directionalcoupler 274, a modulation circuit 276, an oscillator 278, apower-receiving circuit 280, a communication controller 282, and amatching circuit 284.

Note that a frequency band produced by the oscillator 278 is not limitedto a particular band and can be any frequency band as appropriate.Examples of applicable frequency bands include an HF band of 3 MHz to 30MHz (13.56 MHz for example), a UHF band of 300 MHz to 3 GHz (433 MHz,953 MHz, or 2.45 GHz for example), and 135 kHz.

The communication device 270 serves as a so-called reader/writer. Likethe reception circuit 214 in the power-receiving device 200, thepower-receiving circuit 280 can be composed of a plurality of circuitssuch as a low pass filter, an amplification circuit, and a demodulationcircuit.

Wireless communication is carried out in the following manner. Receptionof a signal on a carrier wave or amplitude modulation wave is achievedby using electromagnetic induction between the antenna 272 provided inthe communication device 270 and at least one of the power-receivingresonance coil 104 and the power-receiving coil 108 provided in thepower-receiving device 200, allowing wireless communication.

Specifically, in order to send data from the communication device 270 tothe power-receiving device 200, a carrier wave is first generated withthe oscillator 278 in the communication device 270. A modulation wave isthen superimposed on the carrier wave with the modulation circuit 276 togenerate an amplitude modulation wave. Subsequently, the amplitudemodulation wave is output to the antenna 272 via the matching circuit284 and the directional coupler 274. The amplitude modulation waveoutput to the antenna 272 is received by the power-receiving resonancecoil 104 or power-receiving coil 108 in the power-receiving device 200.The amplitude modulation wave applied to the power-receiving coil 108 isapplied to the reception controller 220 via the directional coupler 202and the reception circuit 214. In this way, the signal on the carrierwave generated in the communication device 270 is sent to thepower-receiving device 200.

In order to send back data from the power-receiving, device 200 to thecommunication device 270, a signal (power) is sent from the receptioncontroller 220 in the power-receiving device 200 to the power-receivingcoil 108 via the modulation transistor 206 and the load modulationelement 204. The signal applied to the power-receiving coil 108 is alsoapplied to the power-receiving resonance coil 104 with theelectromagnetic coupling method. The communication device 270 receivesthe signal applied to the power-receiving coil 108 or thepower-receiving resonance coil 104, at the antenna 272. The receivedsignal is applied to the communication controller 282 via thedirectional coupler 274 and the power-receiving circuit 280. In thisway, the signal from the power-receiving device 200 is sent back to thecommunication device 270.

In this way, the power-receiving device 200 described in this embodimentcan transmit and receive a signal on a carrier wave or an amplitudemodulation wave to/from the antenna 272 via at least one of thepower-receiving resonance coil 104 and the power-receiving coil 108. Inother words, wireless communication can be achieved by using thepower-receiving resonance coil 104 or the power-receiving coil 108.

Although this embodiment describes a structure in which thepower-receiving device 200 and one of the power-transmitting device 250and the communication device 270 are used, as an example, thepower-transmitting device 250 and the communication device 270 may becombined into one device.

As described above, the power-receiving device described in thisembodiment can be used for two systems, a wireless power feeding systemand a wireless communication system, and yields high transmissionefficiency.

This embodiment can be implemented in appropriate combination with anystructure described in the other embodiments.

Embodiment 2

In this embodiment, applications of a wireless power-feeding systemusing the power-receiving device described in the above embodiment aredescribed. Examples of the applications of the wireless power feedingsystem using the power-receiving device according to one embodiment ofthe present invention include portable electronic devices such as adigital video camera and a personal digital assistant (e.g., a mobilecomputer, a cellular phone, a portable game machine, and an e-bookreader). Examples will be described bellow refereeing to drawings.

FIG. 4A shows an example in which a wireless power-feeding system isused for a cellular phone and a personal digital assistant and which iscomposed of a power-transmitting device 700, a power plug 702, and acellular phone 704 including a power-receiving device 706, and acellular phone 708 including a power-receiving device 710. A wirelesspower-feeding system using the power-receiving device described in theabove embodiment is applicable between the power-transmitting device 700and the power-receiving device 706, and between the power-transmittingdevice 700 and the power-receiving device 710.

For example, the power-transmitting device 700 can use the structure ofthe power-transmitting device 250 in FIG. 2 described in Embodiment 1,while the power-receiving device 706 and the power-receiving device 710can use the structure of the power-receiving device 200 in FIG. 2 andFIG. 3 described in Embodiment 1. The power plug 702 is connected to anexternal power source (not shown).

As described above, in this embodiment, a plurality of power-receivingdevices (power-receiving device 706 and power-receiving device 710) canbe used for one power-transmitting device. The wireless power-feedingsystem enables power feeding using the resonance method, and thus canwiden an area where power can be fed and achieve high transmissionefficiency.

The following describes the cellular phone 708 including thepower-receiving device 710 in FIG. 4A in detail with reference to FIGS.4B and 4C. FIGS. 4B and 4C are perspective views of the cellular phone.

FIG. 4B shows the front (display surface) of the cellular phone 708 andillustrates a front housing 711, a speaker part 712, a display part 713,a microphone part 714, a terminal part 716, and a terminal part 722.

FIG. 4C shows the back of the cellular phone 708 and illustrates a backhousing 718, a terminal part 716, a terminal part 722, a camera module723, a lens part 724, and a light 726. The power-receiving device 710and a battery 728 are stored in the back housing 718.

For example, the power-receiving device 710 can use the structure of thepower-receiving device 200 in FIG. 2 and FIG. 3 described inEmbodiment 1. By using the load 212 in FIG. 2 and FIG. 3 described inEmbodiment 1 as the battery 728, power received by the power-receivingdevice 710 can be stored in the battery 728.

Moreover, the power-receiving device 710 stored in the cellular phone708 is capable of wireless communication as well.

As described above, the power-receiving device described in thisembodiment can be used for two systems, wireless power-feeding andwireless communication, and yields high transmission efficiency.

This embodiment can be implemented in appropriate combination with anystructure described in the other embodiments.

Example 1

In Example 1, a wireless power-feeding system with a simple structurewas evaluated by using the power-receiving device in FIG. 1 described inEmbodiment 1. Description will be given with reference to FIGS. 5A to 5Eand FIG. 6.

FIG. 5A is a plan view of a power-receiving device 500, which shows asubstrate 502 viewed from a first surface side. FIG. 5B is a plan viewof the power-receiving device 500, which shows the substrate 502 viewedfrom a second surface side. FIG. 5C is a cross-sectional view takenalong dashed line X2-Y2 in FIGS. 5A and 5B. FIG. 5D is a plan view of apower-transmitting device 550. FIG. 5E is a cross-sectional view takenalong dashed line V-W in FIG. 5D.

The power-receiving device 500 includes the substrate 502, apower-receiving resonance coil 504, a capacitor 506, a power-receivingcoil 508, wiring 510, a socket 512, and a bulb 514.

The substrate 502 is a glass epoxy substrate that measures 4.2 cm wideby 7.2 cm long by 0.7 mm thick. The power-receiving resonance coil 504is made of copper wire and has the following specs: the coil width is 1mm, the coil separation is 1 mm, the number of coil turns is 4, and thecoil thickness is 35 μm. The power-receiving coil 508 is made of copperwire and has the following specs: the coil width is 1 mm, the number ofturns is 1, and the coil thickness is 35 μm. The capacitor 506 is a RFchip capacitor having a capacitance of 59 pF. The wiring 510 isconnected to the power-receiving coil 508 and is electrically connectedto the bulb 514 via the socket 512. Thus, applying power to thepower-receiving coil 508 lights the bulb 514.

The power-transmitting device 550 includes a power-transmitting board520 and a power-transmitting resonance coil 522.

The power-transmitting board 520 is a Styrofoam plate that measures 20cm wide by 20 cm long by 1 cm thick. The power-transmitting resonancecoil 522 is made of copper wire and has the following specs: the coilouter diameter is 15 cm, the coil separation is 1 cm, the number of coilturns is 3, and the coil diameter is 3 mm. Note that coordinates P1 toP9 representing measurement points spaced every 5 cm are written on thepower-transmitting board 520.

The conditions for the power-transmitting device 550 are as follows: thegrid power is 1 W, the oscillation frequency is 15.30 MHz, and theself-resonant frequency of the power-transmitting resonance coil 522 is14.95 MHz.

With the above-described structure, in Example 1, wireless power-feedingwas carried out by the resonance method using the power-receivingresonance coil 504 provided in the power-receiving device 500 and thepower-transmitting resonance coil 522 provided in the power-transmittingdevice 550.

Power from the power-transmitting device 550 is applied to the bulb 514via the power-receiving resonance coil 504, the power-receiving coil508, the wiring 510, and the socket 512 provided in the power-receivingdevice 500. Note that the coordinates P1 to P9 shown in FIG. 5D wereused as evaluation coordinates.

FIG. 6 shows the results of lighting tests on the bulb 514 at P1 to P9.

From FIG. 6, it was confirmed that the bulb 514 could be lit at all thecoordinates P1 to P9. It was also confirmed that the brightness wasapproximately the same at all the coordinates and that, from the resultsof another measurement using the network analyzer N5230A by AgilentTechnologies Inc., the transmission efficiency was as high as 80% to 95%

As described above, it was confirmed that the power-receiving deviceevaluated in Example 1 yielded high transmission efficiency in a widearea.

This embodiment can be implemented in appropriate combination with anystructure described in Example 2 or the embodiments.

Example 2

In Example 2, a wireless communication system with a simple structurewas evaluated by using the power-receiving device in FIG. 1 described inEmbodiment 1. Description will be given with reference to FIGS. 7A to7D.

FIG. 7A is a plan view of a power-receiving device 600, which shows asubstrate 602 viewed from a first surface side. FIG. 7B is a plan viewof the power-receiving device 600, which shows the substrate 602 viewedfrom a second surface side. FIG. 7C is a cross-sectional view takenalong dashed line X3-Y3 in FIGS. 7A and 7B.

The power-receiving device 600 includes the substrate 602, apower-receiving resonance coil 604, a capacitor 606, a power-receivingcoil 608, a wiring 610, and a chip 612.

The substrate 602 is a glass epoxy substrate that measures 4.2 cm wideby 7.2 cm long by 0.7 mm thick. The power-receiving resonance coil 604is made of copper wire and has the following specs: the coil width is 1mm, the coil separation is 1 mm, the number of coil turns is 4, and thecoil thickness is 35 μm. The power-receiving coil 608 is made of copperwire and has the following specs: the coil width is 1 mm, the number ofturns is 1, and the coil thickness is 35 μm. The wiring 610 is connectedto the power-receiving coil 608 and is electrically connected to thechip 612. Thus, applying power to the power-receiving coil 608 operatesthe chip 612.

FIG. 7D is a block diagram showing wireless communication using theelectromagnetic coupling method between the power-receiving deviceaccording to Example 2 and a separately provided communication device,and illustrates the power-receiving device 600, a signal analyzer 620,and a communication device 630 including an antenna 632, a communicationcontroller 634, and a load 636. In the block diagram of FIG. 7D, thecircuits in the power-receiving device and the communication device areclassified according to their functions and shown as independent units.

Note that the communication controller 634 is composed of variouscircuits, such as a low pass filter, a transformer, and a rectifiercircuit, and devices.

The power-receiving device 600 is electrically connected to the signalanalyzer 620 which is capable of conducting signal analysis when thepower-receiving device 600 wirelessly receives data.

In Example 2, an evaluation was conducted of whether the power-receivingdevice 600 received data, with the distance between the power-receivingdevice 600 and the antenna 632 provided in the communication device 630varied between 35 mm to 300 mm and with three values of the output powerof the communication device 630: 0 dBm, 10 dBm, and 20 dBm. Table 1shows the evaluation results.

TABLE 1 Output power [dBm] 0 10 20 Distance between power- 35 X ◯ ◯receiving device and 50 X ◯ ◯ antenna [mm] 70 X ◯ ◯ 90 ◯ ◯ ◯ 130 ◯ ◯ ◯170 Δ ◯ ◯ 210 Δ Δ ◯ 250 X Δ ◯ 300 X Δ Δ

In Table 1, a circle represents the case where the power-receivingdevice 600 receives correct data from the communication device 630, atriangle represents the case where the power-receiving device 600receives any incorrect data from the communication device 630, and across represents the case where the power-receiving device 600 fails toreceive data from the communication device 630.

As shown in Table 1, with an output power of 0 dBm, correct data isreceived with a distance ranging from 90 mm to 130 mm, white partlyincorrect data is received with a distance ranging from 170 mm to 210mm. With an output power of 10 dBm, correct data is received with adistance ranging from 35 mm to 170 mm, while partly incorrect data isreceived with a distance ranging from 210 mm to 300 mm. With an outputpower of 20 dBm, correct data is received with a distance ranging from35 mm to 250 mm, while partly incorrect data is received with a distanceof 300 mm.

Thus, it was confirmed that the power-receiving device shown in Example2 is capable of wireless communication.

This embodiment can be implemented in appropriate combination with anystructure described in Example 1 or the embodiments.

This application is based on Japanese Patent Application serial No.2011-053317 filed with Japan Patent Office on Mar. 10, 2011, the entirecontents of which are hereby incorporated by reference.

What is claimed is:
 1. A power-receiving device comprising: apower-receiving resonance coil on a first surface of a substrate, thepower-receiving resonance coil being configured to generate a firsthigh-frequency voltage by a resonance method; a power-receiving coil ona second surface of the substrate, the power-receiving coil beingconfigured to generate a second high-frequency voltage by usingelectromagnetic induction between the power-receiving coil and thepower-receiving resonance coil; a wireless power-feeding unitelectrically connected to the power-receiving coil; and a wirelesscommunication unit electrically connected to the power-receiving coil,the wireless communication unit comprising: a reception circuitconfigured to receive a signal that has been received by at least one ofthe power-receiving resonance coil and the power-receiving coil; and areception controller configured to control the signal received by thereception circuit, wherein the wireless power-feeding unit and thewireless communication unit are provided over the substrate andintegrated, wherein the power-receiving resonance coil and thepower-receiving coil are overlapped with each other with the substratepositioned therebetween, and wherein the substrate is a flexiblesubstrate.
 2. The power-receiving device according to claim 1, whereinat least one of the power-receiving resonance coil and thepower-receiving coil receives the signal on one of a carrier wave and anamplitude modulation wave by using electromagnetic induction.
 3. Thepower-receiving device according to claim 1, wherein the wirelesspower-feeding unit includes a rectifier circuit configured to rectifythe second high-frequency voltage generated by the power-receiving coil,a converter electrically connected to the rectifier circuit, and a loadconfigured to receive power converted by the converter.
 4. Thepower-receiving device according to claim 1, wherein the wirelesscommunication unit further includes, a modulation transistorelectrically connected to the reception controller, and a loadmodulation element electrically connected to the modulation transistor.5. A system comprising: the power-receiving device according to claim 1;and a power-transmitting device including: a high-frequency powersource; a power-transmitting coil; and a power-transmitting resonancecoil.
 6. A system comprising: the power-receiving device according toclaim 1; and a communication device including: an oscillator; amodulation circuit; a matching circuit; and an antenna electricallyconnected to the matching circuit.
 7. The power-receiving deviceaccording to claim 1, wherein the number of turns of the power-receivingcoil is smaller than that of the power-receiving resonance coil.
 8. Thepower-receiving device according to claim 1, wherein the substrate isone of a glass epoxy substrate, a glass composite substrate, and apaper-phenolic substrate.
 9. A power-receiving device comprising: apower-receiving resonance coil on a first surface of a substrate, thepower-receiving resonance coil being configured to generate a firsthigh-frequency voltage by a resonance method; a capacitor on the firstsurface of the substrate, the capacitor electrically connected to thepower-receiving resonance coil; a power-receiving coil on a secondsurface of the substrate, the power-receiving coil being configured togenerate a second high-frequency voltage by using electromagneticinduction between the power-receiving coil and the power-receivingresonance coil; a wireless power-feeding unit electrically connected tothe power-receiving coil; and a wireless communication unit electricallyconnected to the power-receiving coil, the wireless communication unitcomprising: a reception circuit configured to receive a signal that hasbeen received by at least one of the power-receiving resonance coil andthe power-receiving coil; and a reception controller configured tocontrol the signal received by the reception circuit, wherein thewireless power-feeding unit and the wireless communication unit areintegrated over the substrate, wherein the power-receiving resonancecoil and the power-receiving coil are overlapped with each other withthe substrate positioned therebetween, and wherein the substrate is aflexible substrate.
 10. The power-receiving device according to claim 9,wherein at least one of the power-receiving resonance coil and thepower-receiving coil receives the signal on one of a carrier wave and anamplitude modulation wave by using electromagnetic induction.
 11. Thepower-receiving device according to claim 9, wherein the wirelesspower-feeding unit includes: a rectifier circuit configured to rectifythe second high-frequency voltage generated by the power-receiving coil;a converter electrically connected to the rectifier circuit; and a loadreceiving power converted by the converter.
 12. The power-receivingdevice according to claim 9, wherein the wireless communication unitfurther includes: a modulation transistor electrically connected to thereception controller; and a load modulation element electricallyconnected to the modulation transistor.
 13. A system comprising: thepower-receiving device according to claim 9; and a power-transmittingdevice including: a high-frequency power source; a power-transmittingcoil; and a power-transmitting resonance coil.
 14. A system comprising:the power-receiving device according to claim 9; and a communicationdevice including: an oscillator; a modulation circuit; a matchingcircuit; and an antenna electrically connected to the matching circuit.15. The power-receiving device according to claim 9, wherein the numberof turns of the power-receiving coil is smaller than that of thepower-receiving resonance coil.
 16. The power-receiving device accordingto claim 9, wherein the substrate is one of a glass epoxy substrate, aglass composite substrate, and a paper-phenolic substrate.
 17. Apower-receiving device comprising: a power-receiving resonance coilconfigured to generate a first high-frequency voltage by a resonancemethod; and a power-receiving coil configured to generate a secondhigh-frequency voltage by using electromagnetic induction between thepower-receiving coil and the power-receiving resonance coil, wherein atleast one of the power-receiving resonance coil and the power-receivingcoil receives a signal on one of a carrier wave and an amplitudemodulation wave by using electromagnetic induction, wherein thepower-receiving coil is electrically connected to a wirelesspower-feeding unit and a wireless communication unit, wherein thewireless power-feeding unit includes: a rectifier circuit configured torectify the second high-frequency voltage generated by thepower-receiving coil; a converter electrically connected to therectifier circuit; and a load configured to receive power converted bythe converter, wherein the wireless communication unit includes: areception circuit configured to receive the signal; a receptioncontroller configured to control the signal received by the receptioncircuit; a modulation transistor electrically connected to the receptioncontroller; and a load modulation element electrically connected to themodulation transistor, and wherein the wireless power-feeding unit andthe wireless communication unit are integrated.
 18. A wirelesspower-feeding system comprising: the power-receiving device according toclaim 17; and a power-transmitting device including: a high-frequencypower source configured to generate a third high-frequency voltage; apower-transmitting coil configured to receive the third high-frequencyvoltage; and a power-transmitting resonance coil configured to generatea fourth high-frequency voltage by using electromagnetic inductionbetween the power-transmitting resonance coil and the power-transmittingcoil, wherein the first high-frequency voltage is generated by magneticresonance between the power-transmitting resonance coil and thepower-receiving device.
 19. A wireless communication system comprising:the power-receiving device according to claim 17; and a communicationdevice including: an oscillator configured to generate the carrier wave;a modulation circuit configured to convert the carrier wave into theamplitude modulation wave; a matching circuit configured to subject theamplitude modulation wave to matching; and an antenna electricallyconnected to the matching circuit, wherein the signal on the carrierwave or the amplitude modulation wave is transmitted and received withelectromagnetic induction between the antenna and the power-receivingdevice.
 20. A power-receiving device comprising: a power-receivingresonance coil configured to generate a first high-frequency voltage bya resonance method; and a power-receiving coil configured to generate asecond high-frequency voltage by using electromagnetic induction betweenthe power-receiving coil and the power-receiving resonance coil, whereinat least one of the power-receiving resonance coil and thepower-receiving coil receives a signal on one of a carrier wave and anamplitude modulation wave by using electromagnetic induction, whereinthe power-receiving coil is electrically connected to a wirelesspower-feeding unit and a wireless communication unit, wherein thewireless power-feeding unit includes: a rectifier circuit configured torectify the second high-frequency voltage generated by thepower-receiving coil; a converter electrically connected to therectifier circuit; and a load receiving power converted by theconverter, wherein the wireless communication unit includes: a receptioncircuit configured to receive the signal; a reception controllerconfigured to control the signal received by the reception circuit; amodulation transistor electrically connected to the receptioncontroller; and a load modulation element electrically connected to themodulation transistor, wherein the power-receiving resonance coil andthe power-receiving coil are placed to at least partly overlap with eachother, and wherein the wireless power-feeding unit and the wirelesscommunication unit are integrated.
 21. A wireless power-feeding systemcomprising: the power-receiving device according to claim 20; and apower-transmitting device including: a high-frequency power sourceconfigured to generate a third high-frequency voltage; apower-transmitting coil configured to receive the third high-frequencyvoltage; and a power-transmitting resonance coil configured to generatea fourth high-frequency voltage by using electromagnetic inductionbetween the power-transmitting resonance coil and the power-transmittingcoil, wherein the first high-frequency voltage is generated by magneticresonance between the power-transmitting resonance coil and thepower-receiving device.
 22. A wireless communication system comprising:the power-receiving device according to claim 20; and a communicationdevice including: an oscillator configured to generate the carrier wave;a modulation circuit configured to convert the carrier wave into theamplitude modulation wave; a matching circuit configured to subject theamplitude modulation wave to matching; and an antenna electricallyconnected to the matching circuit, wherein the signal on the carrierwave or the amplitude modulation wave is transmitted and received withelectromagnetic induction between the antenna and the power-receivingdevice.